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Bacterial Biofilms: A Slimy Situation For Medical Devices

March 9, 2000 (Atlanta) -- The very instruments used to keep patients alive
can be a source of deadly infection. Catheters, artificial valves, and other
medical devices are remaining in place longer than ever, and colonization with
slimy, tenacious bacterial biofilms is a growing problem, according to
researchers at a CDC conference on hospital infections.

John W. Costerton, PhD, director of Montana State University's Center for
Biofilm Engineering, explained that biofilms are groups of bacteria growing in
formation. The cells secrete a slimy material that forms a protective barrier
around the colony. Though biofilms have been studied extensively in industrial
settings, only recently has that knowledge been applied to medicine.

Biofilms, often disgusting but generally benign -- dental plaque and shower
curtain mildew are examples -- can pose a serious threat when they form on
medical devices. While a healthy person can safely shower in or even ingest
biofilm, a patient whose urinary catheter or breathing tube is shedding
bacterial colonies is in serious jeopardy, says Costerton.

"The impact of [breathing in] a large lump of bacteria enclosed in a
slime matrix is a very serious challenge to health," he says. Animal
experiments show that lungs can deal with a large number of single bacterial
cells, which are easily destroyed by the immune system, Costerton says,
"but a lump of biofilm always produces infection."

According to presenter Rodney M. Donlan, PhD, a microbiologist with the
CDC's Hospital Infections Program, it may be easier to prevent biofilms from
forming than to get rid of established colonies, because "they are very
tenacious and difficult to remove from a device, even with disinfection."
To that end, prevention research is taking several approaches, ranging from
mechanical to biochemical. Researchers, for example, are working on smoother
surfaces that discourage bacteria from adhering to them.

Biofilm "is not something new," says Michael Bell, MD, a hospital
epidemiologist who is also with the CDC's Hospital Infections Program.
"Organisms have been able to do this nifty thing for a very long time, but
are now becoming important because we are creating a population of susceptible
people [while] increasingly using invasive devices," he says.